AbstractA strategy is described for the detection of protein by using a cationic fluorescent conjugated polymer coupled with exonuclease I (Exo I). Taking streptavidin (SA) as model protein, it is observed that Exo I can digest single-stranded DNA conjugated with biotin and carboxyfluorescein (P1) if SA is absent. This leads to the formation of small nucleotide fragments and to weak fluorescence resonance energy transfer (FRET) from the polymer to P1. If, however, SA is present, the high affinity of SA and biotin prevents the digestion of P1 by Exo I. This results in the sorption of P1 on the surface of the polymer through strong electrostatic interaction. Hence, efficient FRET occurs from the fluorescent polymer to the fluorescent label of P1. Fluorescence is measured at an excitation wavelength of 370 nm, and emission is measured at two wavelengths (530 and 425 nm). The ratio of the two intensities (I530/I425) is directly related to the concentration of SA. Under the optimal conditions, the assay has a detection limit of 1.3 ng·mL−1. The method was also applied to image the folate receptor in HeLa cells, thus demonstrating the versatility of this strategy. Graphical abstractA fluorometric strategy is described for protein detection and cell imaging based on a cationic conjugated polymer (PFP) coupled with exonuclease I (Exo I) trigged fluorescence resonance energy transfer (FRET).

中文翻译：

---

与核酸外切酶 I 偶联的阳离子共轭聚合物：在蛋白质和细胞成像的荧光测定中的应用

摘要描述了使用与外切核酸酶 I (Exo I) 偶联的阳离子荧光共轭聚合物检测蛋白质的策略。以链霉亲和素 (SA) 作为模型蛋白，观察到如果不存在 SA，Exo I 可以消化与生物素和羧基荧光素 (P1) 结合的单链 DNA。这导致小核苷酸片段的形成和从聚合物到 P1 的弱荧光共振能量转移 (FRET)。然而，如果存在 SA，SA 和生物素的高亲和力会阻止 Exo I 对 P1 的消化。这会导致 P1 通过强静电相互作用吸附在聚合物表面。因此，有效的 FRET 从荧光聚合物到 P1 的荧光标记发生。在 370 nm 的激发波长下测量荧光，并且在两个波长（530 和 425 nm）下测量发射。两种强度的比值 (I530/I425) 与 SA 的浓度直接相关。在最佳条件下，检测限为1.3 ng·mL-1。该方法还用于对 HeLa 细胞中的叶酸受体进行成像，从而证明了该策略的多功能性。图形摘要描述了基于阳离子共轭聚合物 (PFP​​) 与外切核酸酶 I (Exo I) 触发荧光共振能量转移 (FRET) 的蛋白质检测和细胞成像的荧光计策略。从而证明了该策略的多功能性。图形摘要描述了基于阳离子共轭聚合物 (PFP​​) 与外切核酸酶 I (Exo I) 触发荧光共振能量转移 (FRET) 的蛋白质检测和细胞成像的荧光计策略。从而证明了该策略的多功能性。图形摘要描述了基于阳离子共轭聚合物 (PFP​​) 与外切核酸酶 I (Exo I) 触发荧光共振能量转移 (FRET) 的蛋白质检测和细胞成像的荧光计策略。